The aims of this project have been to develop in vitro systems for the study of the assembly and folding of the MHC class I molecules. This has been based on the use of in vitro translation and assembly methods to analyze the contribution of the three chains of this complex, the class I heavy chain, beta2-microglobulin, and antigenic peptide. Such studies should not only allow an understanding of this critical step in antigen presentation in the immune system, but should form the basis for an understanding of the folding and assembly of complex multimeric proteins in general.